How robust are in situ observations for validating satellite-derived albedo over the dark zone of the Greenland Ice Sheet?

J.C. Ryan, A. Hubbard, T.D. Irvine-Fynn, S.H. Doyle, J.M. Cook, M. Stibal, J.E. Box

Publikation: Bidrag til tidsskriftArtikelForskningpeer review

27 Citationer (Scopus)

Abstrakt

Calibration and validation of satellite-derived ice sheet albedo data require high-quality, in situ measurements commonly acquired by up and down facing pyranometers mounted on automated weather stations (AWS). However, direct comparison between ground and satellite-derived albedo can only be justified when the measured surface is homogeneous at the length-scale of both satellite pixel and in situ footprint. Here we use digital imagery acquired by an unmanned aerial vehicle to evaluate point-to-pixel albedo comparisons across the western, ablating margin of the Greenland Ice Sheet. Our results reveal that in situ measurements overestimate albedo by up to 0.10 at the end of the melt season because the ground footprints of AWS-mounted pyranometers are insufficient to capture the spatial heterogeneity of the ice surface as it progressively ablates and darkens. Statistical analysis of 21 AWS across the entire Greenland Ice Sheet reveals that almost half suffer from this bias, including some AWS located within the wet snow zone.

OriginalsprogEngelsk
Sider (fra-til)6218-6225
Antal sider8
TidsskriftGeophysical Research Letters
Vol/bind44
Udgave nummer12
DOI
StatusUdgivet - 28 jun. 2017

Programområde

  • Programområde 5: Natur og klima

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